The bad news about testicular cancer is that it is on the increase, particularly among men in their twenties. The good news is that, unlike other adult cancers, it is curable in over 90 per cent of cases - even when the disease has spread.

"I hesitate to use the word cure in terms of cancer," says Stan Kaye, professor of the CRC Department of Medical Oncology at Glasgow University. "But there are now thousands of young men who have been treated successfully for testicular cancer and who, 20 years later, show no sign of any recurrence."

Although rare at the beginning of the century, the incidence of testicular cancer has risen markedly in the last 20-30 years, especially among younger men. It is now the commonest cancer among men aged 20 to 34, with about 1,500 to 2,000 new cases a year.

"We do not know for sure, but it may be this rise is related to an environmental factor such as excess oestrogens, which may affect the foetus growing in the womb," says Professor Kaye.

Testicular cancer is thought to be triggered by something going wrong during foetal development, which would explain why it is sometimes associated with other problems of the male reproductive system - low sperm counts, infertility in men and undescended testicles in boys.

"We think there is another trigger for the cancer 15 to 20 years later, but we do not know what it is. Again, it could be something to do with 20th century living," he adds.

The disease is one of the few cancers to be related to higher social class and is occasionally hereditary. However, Professor Kaye points out that testicular cancer cannot be caused by tight underpants, taking exercise or being kicked - all common myths. "And studies linking it with vasectomy have not held up."

There are two types of testicular cancer. Seminoma, occurs in men in their 30s and 40s and is easier to treat. The second, teratoma, occurs mainly in younger men. Teratoma spreads quite early on in the disease, to the lungs, lymph, abdomen, liver and brain.Thirty years ago it was usually fatal. Today, for the majority of patients, the outlook is very good indeed.

"The big breakthrough came in the mid-1970s when researchers discovered the powerful effects of platinum," says the professor. Using the metal on testicular cancer patients sent cure rates soaring from about 10 per cent to 60-70 per cent. Used in combination with other drugs, the improvement has been even greater.

The platinum drug, cisplatin, is highly toxic. "It was nearly abandoned because of its side effects, but we have now learned to control them. We put the patient on a drip to ensure he has plenty of fluids to avoid kidney damage," says Professor Kaye.

A multinational trial has been set up to see whether it is possible to reduce the standard four courses of treatment to three, and thereby reduce toxic side effects.

One reason cisplatin is extremely effective for testicular cancer is that these cancer cells have a different molecular structure to other adult cancer cells, which makes them unable to resist the drug. "The next big step for researchers is to understand the difference between testicular cancer cells which are killed by chemotherapy and those found in other adult cancers which are resistant to drug treatment. By using gene therapy we may be able to make the latter behave like the former - and become more sensitive to chemotherapy."

The high cure rates in testicular cancer are also thanks to the development of specialist centres - such as the Beatson Oncology Centre in Glasgow - where staff have gained the experience to manage this comparatively rare disease. Another valuable advance is being able to predict which men need aggressive drug treatment and which will do just as well with surgery alone. And the development of sensitive markers in the blood which can detect the disease before it is clinically evident, also means patients with early stage disease who do not have chemotherapy can be carefully monitored for any recurrence.

In addition, by developing a special type of scan, researchers are hoping to be able to predict which men will need further surgery after drug treatment to prevent the cancer returning. At present, this major operation to remove lymph glands in the abdomen is carried out on some 20 to 30 per cent of patients.

For the small group of patients with extensive disease who do not respond well to treatment, the cure rate is about 30 to 40 per cent. CRC researchers are now trying to find more effective treatments by looking at new drugs to add to the current cocktail: clinical trials of the drug Taxol, which was derived from the yew tree and is used in both breast and ovarian cancer, have already started.

Although testicular cancer can be successfully treated, Professor Kaye thinks the psychological effect is often underestimated. "Young men worry about whether the disease or the treatment will affect their fertility," he says.

Losing one testicle, he points out, has no effect on sperm or hormone production. Chemotherapy can cause a temporary effect on fertility, but in the majority of cases it recovers within two or three years and it is possible to store sperm for in vitro fertilisation later, as a precaution.

"Plenty of men who have had testicular cancer go on to have healthy children," says Professor Kaye. "Often these are young men who thought cancer meant they were going to die. The reassuring news is that the vast majority return to live normal, healthy lives."